Molded core filter drier with filter media molded to core

ABSTRACT

This filter-drier for removing moisture from a refrigerant includes a casing having an inlet for receiving refrigerant, an outlet for discharging and a molded core disposed in said casing between said inlet and said outlet. In one embodiment, the molded core includes an outer surface at least in part engaging the inner surface of the casing. The core is held within said casing against axial movement by bonding with said casing or by an indentation protruding into said core or both. In another embodiment, the filter-drier molded core includes a filter media pad bonded to the core, the bond being sufficient to hold the filter media pad in place and eliminate the need for outlet support screens. In another embodiment, the filter-drier includes a hollow cylindrical core having a filter media bonded to the core and defining a filter media lined passage, the core being held in place by end plates having opposed axial check valves and offset check valves. This filter-drier is suitable for reversible operation in a heat pump system.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] Continuation-in-part of Utility Application No. 10/057,207 filedJan. 25, 2002.

BACKGROUND OF THE INVENTION

[0002] This invention relates generally to filter-driers forrefrigeration systems and particularly to a casing and a moldedfilter-drier core having superior structural characteristics ofattrition resistance, strength and permeability while being held firmlyin place by structural cooperation between the casing and the core.

[0003] Filter-driers are used in refrigeration systems to filter solidcontaminants and to remove soluble contaminants from the refrigerant andlubricant. The three general types of construction of filter-driers areloose fill, compacted bead, and molded core.

[0004] In a loose fill design, the desiccant is captured within meshscreens to prevent the desiccant beads from escaping into the system.The beads form a desiccant bed trapped between the shell and meshscreens, however, within the desiccant bed the beads are only looselyheld. Flow of refrigerant through the desiccant bed or vibration of thefilter-drier shell from other sources results in undesirable movement ofthe individual beads within the bed. Contact of the desiccant beads withthe shell, mesh screens, or other desiccant beads can lead to attritionof the desiccant beads. As attrition of the beads progresses, thedesiccant fines escape the mesh screens and circulate in therefrigerating system.

[0005] Compacted bead designs use desiccant beads similar to the loosefill design but incorporates perforated metal and mesh screens, filterpads, and springs to compact the desiccant bed. The compaction of thedesiccant bed restricts the movement of the individual beads compared toa loose fill design and reduces the risk of attrition, however, thisdesign does not eliminate attrition.

[0006] A molded core unit consists of a molded desiccant block held inplace with support screens, filter pads, and springs. The molded core ismade of smaller granules of desiccant than the loose fill or compactedbead design. The desiccant granules are bonded together using an organicor inorganic binder to form a solid shape. This design preventsattrition of the desiccants by not allowing movement of the granules.

[0007] Typically, shells to contain the desiccants in a filter-drier areeither welded steel shell consisting of steel tubing and/or stampedpieces welded together to form a sealed shell. Alternatively, copperspun shells may be used in which copper tubing is reduced to a specificfitting size. Prior to welding a steel shell or spinning to reduce thediameter of the copper tubing, the internal parts consisting componentssuch as perforated screens, mesh screens, filter pads, desiccant, andsprings are assembled. The purpose of the screens and springs is tocontain the desiccant beads or desiccant core.

[0008] Known filter-drier units having molded cores and incorporatedherein by reference, are disclosed in U.S. Pat. No. 2,556,292, U.S. Pat.No. 5,440,898, U.S. Pat. No. 5,562,427 and U.S. Pat. No. 2,551,426. U.S.Pat. No. 2,556,892 discloses a core formed from molded discs and U.S.Pat. No. 5,440,898 disclosed a molded core which is strengthened by theuse of fibers. In both cases, the core is spaced from an outer metalcasing and held in place by a lateral support system at each end. U.S.Pat. No. 5,562,427 discloses a copper casing with longitudinally spacedgrooves formed to hold a preformed solid core. The grooves are formed bythe drawing process but are at each end of the core. U.S. Pat. No.2,551,426 discloses a preformed block of drying agent which is supportedby longitudinally spaced internal protrusions.

[0009] The present system overcomes the need for support systems forholding the core in place in a manner not disclosed in the known priorart.

SUMMARY OF THE INVENTION

[0010] This molded core filter drier does not require additional partsto hold the core in place within the casing and the core is formedwithin the casing and held within the casing by structural cooperationbetween the casing and the core. The binder used in the molded coreserves to bind the desiccants together and, in addition, binds thedesiccant core to the casing. Thus movement between the core and thecasing is prevented thereby substantially eliminating desiccantattrition. It is an advantage to provide a filter bonded to the core.

[0011] This filter-drier is for drying refrigerant circulated in arefrigeration system by removing moisture therefrom, and comprises acasing having an inlet for receiving refrigerant, and an outlet fordischarging refrigerant. The casing includes opposed end portions and anintermediate portion disposed between said end portions. A molded coreincluding inlet and outlet end portions is provided disposed in saidcasing between said inlet and outlet and receiving flow of refrigeranttherethrough and holding means is provided between the casing and saidcore for holding the core in place within the casing and a filter isbonded to the core, as by molding.

[0012] It is an aspect of this invention to provide that the filter isbonded to at least one of said molded core end portions.

[0013] It is another aspect of this invention to provide the filter isbonded to said molded core outlet end portion.

[0014] It is still another aspect of this invention to provide that thecore includes a passage having a closed end proximate the inlet portionand an open end proximate the outlet portion; and the passage is lined,at least in part, with the filter.

[0015] It is yet another aspect of this invention to provide that thecore passage includes inclined sides.

[0016] It is an aspect of this invention to provide that the corepassage is generally conical.

[0017] It is yet another aspect of this invention to provide that thecore passage open end includes an annular portion, and the filter isbonded to said annular portion.

[0018] It is an aspect of this invention to provide a filter-driercomprising a casing having an inlet for receiving refrigerant, and anoutlet for discharging refrigerant. The casing includes opposed endportions and an intermediate portion disposed between said end portionsand having an inner surface. A molded core is provided including anouter surface and inlet and outlet end portions disposed in said casingbetween said inlet and outlet and receiving flow of refrigeranttherethrough ;and holding means is provided between said casing innersurface and said core outer surface for holding the core in place; and afilter media is molded to the core.

[0019] It is another aspect of this invention to provide that theholding means includes at least one protrusion from the inner surface ofthe casing engaging the outer surface of the core to inhibit axialmovement of the core.

[0020] It is still another aspect of this invention to provide that theholding means includes bonding means between the inner surface of thecasing and the outer surface of the core to inhibit axial movement ofthe core.

[0021] It is an aspect of this invention to provide a method ofmanufacturing a filter-drier having a tubular casing and a desiccantcore between an inlet and an outlet comprising the steps of: providing atubular mold; providing a mold base associated with the tubular mold;placing a filter media on the mold base; depositing a desiccant/bindermix within the mold and over the filter media to bond the filter mediato the core; providing a mold cap over the desiccant core; and removingthe mold base and cap when the core has set.

[0022] It is another aspect of this invention to provide a methodwherein the filter media is disposed at the outlet of the core and toprovide the additional step of compressing the desiccant/binder with thecap.

[0023] It is an aspect of this invention to provide that the filtermedia is molded to the core.

[0024] This filter-drier is relatively inexpensive and simple tomanufacture and is particularly effective for its intended purpose.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 is a diagrammatic view of a refrigeration system utilizinga filter-drier assembly in the liquid line and in the suction line;

[0026]FIG. 2 is a longitudinal cross-sectional view of the filter-drierassembly;

[0027]FIG. 3 is an enlarged fragmentary view of the holding indentation;

[0028]FIG. 4 is an end view of the filter-drier assembly;

[0029]FIG. 5 is a cross-sectional view taken on line 5-5 of FIG. 2; and

[0030]FIG. 6 is a cross-sectional view taken on line 6-6 of FIG. 2.

[0031]FIG. 7 is a longitudinal cross-sectional view of a modifiedfilter-drier assembly;

[0032]FIG. 8 is a cross-sectional view taken on line 8-8 of FIG. 7;

[0033]FIG. 9 is a longitudinal cross-sectional view of another modifiedfilter-drier assembly;

[0034]FIG. 10 is a cross-sectional view taken on line 10-10 of FIG. 10;

[0035]FIG. 11 is a longitudinal cross-sectional view of another modifiedfilter-drier assembly;

[0036]FIG. 12 is a cross-sectional view taken on line 12-12 of FIG. 11;

[0037]FIG. 13 is a cross-sectional view taken on line 13-13 of FIG. 11;

[0038]FIG. 14 is a diagrammatic view of a heat pump utilizing thefilter-drier of FIGS. 11-13 in the reversing liquid line;

[0039] FIGS. 15-17 are schematics illustrating the first, second andthird stages of forming the filter-drier of FIG. 9; and

[0040] FIGS. 18-20 are schematics illustrating the first, second andthird stages of forming the core of the filter-drier of FIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0041] Referring now by reference numerals to the drawings and first toFIG. 1, it will be understood that one or more filter-drier assemblies10 are used in a refrigeration system 1 which includes a compressor 2,an evaporator 3, a condenser 4 and an expansion device 5 such as athermostatic expansion valve.

[0042] In the embodiment shown, a hot gas line 6 is provided between thecompressor 2 and the condenser 4. A liquid line 7 is provided betweenthe condenser 4 and the expansion device 5 and a suction line 8 isprovided between the evaporator 3 and the compressor 2. A firstfilter-drier assembly 10 is disposed in line 7 between the condenser 4and the expansion device 5. Also, in the embodiment shown, a secondfilter-drier assembly 10 is disposed in the suction line 8 between theevaporator 3 and the compressor 2.

[0043] More specifically, the filter-drier assembly 10 includes a casing12 and a molded core 30. The casing 12 includes inlet and outlet nozzlefittings 16 and 18, and a cylindrical intermediate portion 20. As shownin FIGS. 3 and 6, the intermediate portion 20 includes an inwardlyprotruding U-shaped circular indention 22, located closer to the outlet18 than the inlet 16, in the embodiment shown, and opposed funnel-shapedtransition portions 24.

[0044] The molded core 30 is disposed within the casing 12 and includesa cylindrical portion 32 disposed in engaging relation to thecylindrical casing portion 20. The molded core 30 may also include afrusto-conical portion 34 at the inlet end spaced from the casing and apassage 36 having a closed end 38 and an open end 40 disposed at theoutlet end of the casing.

[0045] The permeable molded desiccant core 30 includes a binder and ismolded in place within the casing after formation of the circularindentation 22 but before the transition portions 24 are formed. In theembodiment shown, the relatively short tubular casings 12 may beprovided by sections cut from a relatively long copper tube. In thiscase the indentations may be created in the elongate tube prior tocutting the tube into sections. Also, in the embodiment shown, thetubular casing is formed of spun copper and the transition portions arecreated by the spinning process. The core 30 is molded in place and thecylindrical portion 32 of the core outer surface is in adhering contactengagement with the inside wall of the cylindrical casing portion 20after the core is molded. Because of this structural arrangement ofparts, the circular indentation 22 is molded into the core materialwhich is molded in place about the indentation. Following the coremolding procedure the casing transition portions 24 are reduced to thegenerally funnel-shaped configuration shown and the inlet and outletfittings 16 and 18 are emplaced at opposite ends.

[0046] With the structural arrangement of casing and core parts shown,the molded core is held in place by bonding between the outer surface ofthe core and the inner surface of the casing, said bonding constitutinga holding means. In addition, the provision of the circular indentation22 holds the core in place mechanically by the tongue and groove effectbetween the casing 12 and the molded core 30 and constitutes anotherholding means. Thus, the core may be held by one of two holding means orby both holding means.

[0047] Molding the desiccant core around the indentation utilizes thestrength of the molded core and greatly increases the force required tomove the core 30 within the casing 12. In the event that the bondbetween the molded core and the casing, which is provided by the binder,is destroyed during the production process or during installation, themechanical retention provided by the indentation is sufficient toprevent movement of the core within the casing.

[0048] The configuration and permeability of the molded core areoptimized to ensure sufficient refrigerant flow characteristics,desiccant core weight and filtration performance.

[0049] In operation, refrigerant flowing through the system is receivedinto the casing at the inlet 16, and enters the core 30 at the surfaceprovided by the frusto-conical portion 34. The refrigerant enters thepassage 36 through the core frusto-conical portion 34 and thecylindrical portion 32 as indicated by the arrows and is discharged atthe outlet 18. It will be understood that while the frusto-conicalportion 34 has some advantage in that a greater surface area is providedfor receiving the refrigerant, the core 30 may be formed without afrusto-conical end.

[0050] A modified filter-drier 110 is shown in FIGS. 7 and 8 which issimilar to the filter-drier 10 shown in FIGS. 1-6, in that it includes acasing 112 having a molded core 130 held in place by bonding between theinner surface of the casing 112 and the outer surface of the core 130,and by the provision of a circular indentation 122 which holds themolded core 130 in place mechanically by the tongue and groove effectbetween the casing 1 12 and the core 130. For this reason, similar partsare given similar identification numerals with the addition of a prefixnumeral “1”. The modified filter-drier 110 is different from thefilter-drier 10 in that it includes a filter media pad 150 at the outletof the core 130 bonded to said core. The strength of the bond betweenthe filter pad 150 and the core 120 ensures that the filter pad 150 isheld securely in place and eliminates the need for outlet supportscreens. The refrigeration system, shown in FIG. 1 is unchanged.

[0051] More specifically, and referring again to the embodiment shown inFIGS. 7 and 8, the filter-drier assembly 110 includes a casing 112 and amolded core 130. The casing 112 includes inlet and outlet nozzlefittings 116 and 118 and a cylindrical intermediate portion 120. Theintermediate portion 120 includes an inwardly protruding indentation 122located between the outlet 118 and the inlet 116 and the casing 112includes opposed funnel-shaped transition portions 124.

[0052] The molded core 130 is disposed within the casing 112 and iscylindrical in configuration having generally flat circular ends 138 and140 providing an inlet and an outlet for the circular core.

[0053] The permeable molded desiccant core 130 includes a binder and ismolded in place within case 112 after the formation of the circularindentation 122 but before the transition portions 124 are formed. Thecore 130 outer surface is in adhering contact engagement with the insidewall after the core 130 is molded. As with the previous embodiment, thecore 130 may be held in place mechanically by the casing groove 122 orby the adhesive effect of the bond between the molded core 130 and thecasing 112 or both.

[0054] Distinguishing between the previous embodiment shown in FIGS.1-6, the filter-drier 110 includes a circular pad 150 of filter mediabonded to the molded core 112. In the embodiment shown, this pad 150 isdisposed on the flat outlet end 140 of the molded core 130. Because ofthis preferred arrangement there is no compressive force from the flowof refrigerant on the pad 150 and therefore no tendency for flow to berestricted by an effective reduction of the thickness of the pad, itbeing understood that compression of a filter pad 150 alters the flowand filtration characteristics. Since the filter pad 150 is notcompressed, the original characteristics of the pad are retained. Thereis also an advantage in the use of a pad at the inlet end 138, in lieuof or as well as, the outlet end, because, to whichever end of the coreit is bonded it eliminates the need for filter pads held in place bymetal screen or similar devices. The use of a filter media molded to thedesiccant core may be used in the liquid or suction line of therefrigeration system shown in FIG. 1.

[0055] A second modified filter-drier assembly 210 is shown in FIGS. 9and 10. In this embodiment, the reference numerals are similar forsimilar parts with the addition of the numeral “2”. As shown, thefilter-drier assembly 210 includes a casing 212 similar to that shown inthe previous embodiment but the core 230 is different, in that itincludes a frusto-conical portion 234 at the inlet end and a recessedconical portion 236 and an annular portion 240 at the outlet end. Thisarrangement provides that the inlet and outlet areas of the core 230,are increased. More specifically, the filter media pad 250 conforms tothe shape of the recessed conical portion 236 and annular portion 240,which helps to optimize the flow characteristics since the filter pad250 is not under compression.

[0056] A third modified filter-drier assembly 310 is shown in FIGS.11-13. This assembly is intended for use in the reversing liquid line ofa heat pump of the type shown in simplified form in FIG. 14. The heatpump 300 requires a filter-drier assembly having a reversibleconstruction providing two-way flow capability. The heat pump 300includes a compressor 301, an evaporator 302, a condenser 303 and twothermal expansion valve assemblies 304, each having a check valve 305.The reversing liquid line 306 between two thermal expansion valveassemblies 304 includes a heat pump filter-drier which is shown indetail in FIGS. 11-13.

[0057] The reversible filter-drier 310 includes a two-part casing 320consisting of opposed half-portions 322 and 324 connected at a joint 326by welding, or otherwise. Supported within the casing 320 by circularend plates 340 and 341 is a hollow cylindrical core 330 defining afilter lined passage 332. The circular end plates 340 and 341 eachincludes an axially aligned check valve 342 and an offset check valve344. The axially aligned check valves include a tubular member 346welded, or otherwise attached, to a central opening 348 in each endplate 340 and 341. The tubular member 346 includes an annular abutment360 at the outer end supporting a spring 362 and a coined abutment 364at the inner end supporting a ball 366. The offset check valves 344 aresimilar to check valve 342 in that they include a tubular member 346welded, or otherwise attached, to an offset opening 368 in each endplate 340 and 341. The tubular member 346 includes an annular abutment360 at the inner end supporting a spring 362 and a coined abutment 364at the outer end support a ball 366. There is a gap 370 between eachinlet and outlet fitting 316 and 318, respectively, and the associatedaxially aligned tubular member 342 and 344, respectively.

[0058] The cylindrical core 320 includes a filter media 350 disposedabout the core 320 having a tubular portion 352 and annular end portions354 and 356. The core and filter media combination 320, 350 is supportedbetween the axially aligned check valves 342 and 344.

[0059] In operation, in the position shown in FIG. 11, refrigerantenters the inlet 316 and passes radially outwardly through the gap 370to open check valve 344 and then flows radially inwardly through thetubular core 330 and the filter lining 350 into the passage 332 alignedwith the check valves 342 and out through the outlet 318. In the reverseoperation, the procedure is identical with the outlet becoming theinlet.

[0060] As well-known to those skilled in the art, the desiccants mostcommonly used in filter-driers are molecular sieve, activated aluminaand activated carbon. Less commonly used is silica gel. Binders may beorganic, typically polymers such as epoxy or phenolic, or inorganic suchas phosphates or silicate. The core porosity, as is well known to thoseskilled in the art, depends upon the particular desiccant and binderselected and the flow rate required and other readily determinablefactors.

[0061] The outlet filter media is typically a woven or wound fiber suchfiber glass, polyester and polypropylene. It is desirable to use afilter media material that is manufactured to eliminate loose fibersthat could escape into the system rather than a media that containsloose fibers.

[0062] Preferably, the filter media is bonded to the desiccant coreduring the molding process and additional binder is not required. Thebonding could be accomplished in a second step but is less desirablebecause it requires an additional step in the process than when it ismolded to the core.

[0063] As will be readily understood by those skilled in the art thetype and density of filter media is chosen based on factors such ascompatibility with refrigerants and lubricants, durability, andfiltration characteristics. A filter mesh of 5-80 microns with a pad orfilter element depth of about 0.1 inch is satisfactory for mostfilter-drier purposes but the specific purpose for which the filtermedia is to be used will enable those skilled in the art to determinethe filter mesh and depth appropriate for that purpose.

[0064] FIGS. 15-17 and FIGS. 18-20 are schematics illustrating stages inthe method of forming the filter-driers cores shown in FIGS. 9 and 11,respectively.

[0065] Referring first to FIGS. 15-17, it will be understood from FIG.15 that the mold assembly 400 initially consists of a bottom mold base402 which determines the shape of the outlet of the core, a side tube404, having a holding ring 405, which determines the diameter of thecore, and a top mold cap 406 which determines the shape of the inlet ofthe core. In the process of forming the core, the side tube 404 isplaced on the mold base 402. In the embodiment shown, a preformed,conical filter media 250 is placed over the mold base prior to addingthe desiccant/binder mix to firmly bond the filter media to the core. Asshown in FIG. 16, the desiccant/binder mix is deposited into the tube toa level less than that of the frusto-conical outlet. The mold cap 406 isthen placed inside the tube and the desiccant mix is compressed, asshown in dotted outline, in FIG. 16 to a marker stop 408 to complete themolded core as shown in FIG. 17 to eliminate unnecessary voids in thecore and ensure a good bond with the filter media. The core binder isallowed to set and the mold base 402 and cap 406 are removed from themold. Where the core is intended to be molded to the shell, the sidetube 404 becomes the shell and is not removed from the core but ratherbecomes part of the filter-drier. As shown in FIG. 17, the reducedtransitional end portions of the side tube 404 are formed to completethe filter-drier shell after the base mold 402 and cap mold 406 areremoved.

[0066] Referring to FIGS. 18-20, it will be understood from FIG. 18 thatthe mold assembly is for manufacturing a filter-drier desiccant core fora heat pump of the type shown in FIG. 11. The mold assembly 500initially consists of a mold base 502, a center post 504 and a tubularmold 506. Filter media portions in the form of a tube 352 and an annularend 354 are placed over the mold base 502 and the center post 504 thatforms the inner diameter of the core within the tube 506 that forms theouter diameter of the core. As shown in FIG. 19, the desiccant/bindermix 505 is added to a height slightly greater than the finished lengthof the core and an annular piece of filter media 356 is placed in themold prior to the fitting of a mold cap 508 which is then compressed tothe finished size of the filter-drier core to eliminate unnecessaryvoids in the core and ensure a good bond with the filter media. The corebinder is allowed to set and the mold base 502, the center post 504, thetube 506 and the mold cap 508 are removed leaving the core with thefilter media elements in place as shown in FIG. 20, ready for use in theheat pump filter drier shown in FIG. 11.

[0067] The invention has been described by making reference to apreferred filter-drier core construction. However, the details ofdescription are not to be understood as restrictive, numerous variantsbeing possible with the principles disclosed and within the fair scopeof the claims hereunto appended.

I claim as my invention.
 1. A filter-drier for drying refrigerantcirculated in a refrigeration system by removing moisture therefrom, thefilter-drier comprising: a casing having an inlet for receivingrefrigerant, and an outlet for discharging refrigerant, the casingincluding opposed end portions and an intermediate portion disposedbetween said end portions; a molded core including inlet and outlet endportions disposed in said casing between said casing inlet and outletand receiving flow of refrigerant therethrough; holding means betweensaid casing and said core for holding the core in place; and a filterbonded to the core.
 2. A filter-drier as defined in claim 1, wherein:the filter is bonded to at least one of said molded core end portions.3. A filter-drier as defined in claim 2, wherein: the filter is bondedto said molded core outlet end portion.
 4. A filter-drier as defined inclaim 2, wherein: the core includes a passage having a closed endproximate the inlet portion and an open end proximate the outletportion; and the passage is lined, at least in part, with the filter. 5.A filter-drier as defined in claim 4, wherein: the core passage includesinclined sides.
 6. A filter-drier as defined in claim 4, wherein: thecore passage is generally conical.
 7. A filter-drier as defined in claim4, wherein: the core passage open end includes an annular portion, andthe filter is bonded to said annular portion.
 8. A filter-drier fordrying refrigerant circulated in a refrigeration system by removingmoisture therefrom, the filter-drier comprising: a casing having aninlet for receiving refrigerant, and an outlet for dischargingrefrigerant, the casing including opposed end portions and anintermediate portion disposed between said end portions and having aninner surface; a molded core including an outer surface and inlet andoutlet end portions disposed in said casing between said inlet andoutlet and receiving flow of refrigerant therethrough; holding meansbetween said casing inner surface and said core outer surface forholding the core in place; and a filter media is molded to the core. 9.A filter-drier as defined in claim 8, wherein: the holding meansincludes at least one protrusion from the inner surface of the casingengaging the outer surface of the core to inhibit axial movement of thecore.
 10. A filter-drier as defined in claim 8, wherein: the holdingmeans includes bonding means between the inner surface of the casing andthe outer surface of the core to inhibit axial movement of the core. 11.A method of manufacturing a filter-drier having a tubular casing and adesiccant core between an inlet and an outlet comprising the steps of:providing a tubular mold; providing a mold base associated with thetubular mold; placing a filter media on the mold base; depositing adesiccant/binder mix within the tubular mold and over the filter mediato bond the filter media to the core; providing a mold cap over thedesiccant core; and removing the mold base and cap when the core hasset.
 12. A method of manufacturing a filter-drier as defined in claim11, wherein: the filter media is disposed at the outlet of the core. 13.A method of manufacturing a filter-drier as defined in claim 11,including the additional step of: compressing the desiccant/binder withthe cap.
 14. A method of manufacturing a filter-drier as defined inclaim 11, wherein: the filter media is molded to the core.